1. Field of the Invention
The present invention relates to a method and system for generating voltages higher than those available from the power supply to an integrated circuit (IC) chip.
2. Description of Related Art
Oxide-type electronic fuses or antifuses have recently been introduced into semiconductor technology, and can require a programming voltage which is higher than the power supply voltage (Vext) normally available to and used by the integrated circuit chip. Antifuse programming is typically done at manufacturing test and may require a high voltage generator to function for 10 seconds or less. Most chips have been traditionally powered by a 5 v power supply, and such power supply voltages are now moving to lower, to the approximately 3 v range, e.g., 3.3 v and as low as 2.7 v. The voltage that is needed to program antifuses is about 6-10 v. These high voltages need to be supplied either from a source off-chip, e.g., by way of a special pin, which has its own set of problems, or by generating the voltage from a source on-chip. High voltage can be supplied from off-chip but requires special electrostatic device (ESD) protection circuits to admit voltage levels usually shunted by conventional ESD devices. While an oscillator and multistage pump may be used to generate 10 v on-chip, such a device requires a relatively large amount of area on-chip, which is not desirable.
In addition to generating a voltage to program electrical fuses, other specific applications may need higher voltages than those available on-chip, such as generating a reference voltage, providing a means to charge a battery and any application that would require a higher voltage that uses low power. It would be advantageous to be able to generate voltages on an integrated circuit chip that are 2-4 times the voltage available from the normal chip power supply, and to do so with a compact device.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method and system for generating voltages on an integrated circuit chip which are higher than those available on-chip from the chip power supply.
It is another object of the present invention to provide a system for generating higher voltages on an integrated circuit chip which is relatively compact.
A further object of the invention is to provide a method and system for generating higher voltages on an integrated circuit chip which may be used to program antifuses.
It is yet another object of the present invention to provide a method and system for generating higher voltages on an integrated circuit chip which may be used for higher voltage applications that use low power.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one skilled in the art, are achieved in the present invention which is directed to, in a first aspect, a method of generating higher voltage on an integrated circuit chip from a power supply available to the chip comprising providing an inductor on or in contact with the integrated circuit chip; driving current from the power supply through the inductor; and interrupting the current through the inductor at desired time intervals to create voltage spikes above the power supply voltage.
Preferably, the integrated circuit chip includes a lead frame connecting the integrated circuit chip to an integrated chip package, and the inductor comprises a portion of the lead frame. The current may be driven through a plurality of transistors on the integrated circuit chip, and a clock may be connected to one of the transistors to interrupt the current. The method may further include rectifying, collecting and storing the voltage spikes on a capacitor and rectifier disposed on the integrated circuit chip.
In operation, positive and negative voltage spikes are created by interrupting the current, and the method may further include employing diodes on the integrated circuit chip to shunt away the negative spikes to ground. A stacked diode clamp on the integrated circuit chip may be used to limit the higher voltage generated. The voltage spikes may generate a voltage about two or more times the voltage of the power supply available to the chip. The integrated circuit chip may include an electrical fuse and/or a battery, and the higher voltage generated by the voltage spikes may be used to program the fuse on the chip and/or charge the battery.
In a related aspect, the present invention is directed to a voltage generator for an integrated circuit chip comprising an integrated circuit chip with a power supply having a voltage available to the chip; an inductor on or in contact with the integrated circuit chip electrically connected to the power supply through which current is driven; and a clock adapted to interrupting current flowing from the power supply through the inductor at desired time intervals to create voltage spikes above the power supply voltage.
Preferably, the integrated circuit chip includes a lead frame connecting the integrated circuit chip to an integrated chip package, and the inductor comprises a portion of the lead frame. The voltage generator may further include transistors disposed on the integrated circuit chip and connected to the inductor through which current is driven, and the clock may be connected to one of the transistors to interrupt the current driven through the transistors. The voltage generator may also include a capacitor and rectifier disposed on the integrated circuit chip adapted to collect and store the voltage spikes. Diodes disposed on the integrated circuit chip may be adapted to shunt away to ground negative voltage spikes created by interrupting the current, and a stacked diode clamp disposed on the integrated circuit chip may be adapted to limit the higher voltage generated. The voltage spikes generate a voltage bout two or more times the voltage of the power supply available to the chip. Where the integrated circuit chip includes an electrical fuse and/or a battery, the fuse on the chip may be adapted to be programmed and/or the battery may be charged by the higher voltage generated by the voltage spikes.